This invention relates to a damped mount incorporating a resilient block and used for connecting two members while isolating and/or controlling the transfer of motion, and particularly motion due to vibration or shock, between these members. Mounts of the general type are described in U.S. Pat. Nos. 3,147,964; 3,508,745; 3,642,268; and 3,698,703.
The earlier type of mount disclosed in said U.S. Pat. No. 3,147,964, utilizes primarily the directed energy absorbing characteristics of a compressed rubber bushing to control the transmission of vibration between two members, and also to provide a certain amount of shock isolation in the mounting of one mechanical member to another, while still mechanically connecting the members as desired. These members can be any of a vast variety of devices such as different parts of mechanisms or vehicles, supports for machinery, and packaging supports for large masses. Of particular interest are the connections of chassis and body parts in vehicles and/or the mounting of an engine in an automobile, which requires control and isolation in six different degrees of freedom, namely motion along X, Y and Z axes and rotation about these axes, namely roll, pitch and yaw. In this area of application alone, the modern demands for vibration control/isolation and adequate support and anchoring present sophisticated mount design requirements which are aggravated by the need to accomodate some degree of misalignment which is to be expected in mass production systems.
The aforementioned '268 and '703 patents disclose such mounts wherein the action of a resilient (such as rubber) member incorporated in the mount is modified by the placement of a damping liquid in cavities located on opposite sides of and within the resilient member. These cavities are connected through a passage which restricts the flow of the liquid between the cavities, thus further damping the motion of the resilient member along a plane extending through the two cavities. Mounts such as these are designed to handle predetermined loads and damp at certain predetermined frequencies, but they are unable to interact with changing conditions involving the supported member, such as an engine undergoing operating change due to varying load, etc. An interactive mount, on the other hand, can respond to signals indicating changes in engine operation, or changes in suspension demands, and change its spring rate, or its damping capacity, temporarily to accomodate changes of a temporary nature accompanying vehicle operations.
Various types of interactive engine mount and suspension components and systems have been used and/or described in publications related to the automotive industry. These are characterized by having high/low or hard/soft controls, e.g. selectable between two different characteristics, and also by use of mount structures which are direction sensitive to applied loads. The selection of higher or lower damping characteristics has been achieved by choosing between two different sizes of orifice in a bleed passage between hydraulic chambers in a mount, or by changing the opening of a valve in a strut-type mount. The mount structures used in these prior art devices are generally strut-type and have poor tolerance for forces applied off the axis of the strut. Typical such devices and systems are disclosed in SAE Technical Papers No. 840258 and 840259, presented at an International Congress & Exhibition in Detroit, Mich. and Copyright 1984 by the Society of Automotive Engineers, Inc., and in Machine Design magazine, Nov. 11, 1982, pages 86,87, describing a Lucas Girling Ltd. system.